Where is your antifreeze going if its not leaking?

Check to see if it is mixing with engine oil

Run engine to normal operating temperature and remove oil dipstick, let a drop fall on hot part of engine - oil will smoke coolant will "sizzle"

If so could be a sign of a bad head gasket

It's not going anywhere in a Type 1 Beetle because we never used antifreeze in aircooled engines.

In a New Beetle, it could be going one of three places. In ascending order of dread:

You could have a leak you don't know about. Do you smell antifreeze inside the car? Heater cores do spring leaks occasionally. (Changing one is an awful job. Hope it's not that.) Heater hoses leak. Little pinholes you can't even see will cause leaks you can't find.

You could have a bad head gasket.

Or you could have a cracked block.